The present invention relates to a device for producing compressed bales from compressible pressed product pieces, in particular residues, such as used paper, used paper-board containers, plastic films or empty plastic bottles, each compressed bale produced having an essentially cuboid form with edge lengths A, B and C. The device comprises a press housing having at least one press chamber and a press shield that can be moved in the press chamber in the press direction and back by means of a mechanical drive.
Baling presses for the different applications are equipped with a press shield that can be moved either in vertical direction or in horizontal direction and have been known on the market for many years. Usually, the compressed bales produced have a cuboid or cubic form wherein the dimensions of the edge lengths of the compressed bales are, in particular, dependent on the transportation means which are used to transport the compressed bales after the production thereof. If they are to be transported on europallets, the width and depth of the bales are, appropriately, adjusted to the base area of the pallet and will then have a size of approximately 800 mm×1,200 mm. To ensure that the bale remains protected from overturning, its maximum height is approximately 1,200 mm. If the bales are to be transported in containers, a size of the bales that is usual in the market is approximately 1,100 mm×1,100 mm×1,100 mm, i.e. a cubic form. In its dimensions, the press chamber of the presses for producing such compressed bales is designed according to the dimensions of the compressed bales to be produced, and the cross-sectional area of the press chamber will then have dimensions that correspond to the width and depth of the compressed bales.
If presses are equipped with a press shield that can be moved in vertical direction, the press shield is driven either by one or by a plurality of hydraulic cylinders. Known vertical single-chamber baling presses are filled through a fill chamber or a door that closes the entire press chamber and is partially opened during filling. The pressed product pieces to be compressed are inserted below the press shield that is, then, it its uppermost position, through the door opening and into the press chamber and are, if necessary, placed onto pressed product that has already been compressed. Once a filling region of the press chamber is filled such that new pressed product does not fit in any more, the door is closed and the movable press shield moves toward a floor of the press chamber that is limiting the press chamber at its bottom. In order to realize bale weights that are as high as possible, large-dimensioned hydraulic cylinders are used today, said cylinders exerting a large press force onto the pressed product to be compressed to form a compressed bale if the pressure is appropriate.
If baling presses are equipped with a press shield that can be moved in vertical direction, the guide of the press shield in the press chamber presents a problem that cannot be neglected. There are different realized guides of the press shield in the press chamber, but all of these guides were, in practice, not able to prevent the press shield or the hydraulic drive elements (hydraulic cylinders) from being damaged, in particular in case of an irregular filling of the press chamber. A further problem caused in baling presses with a press shield that can be moved in vertical direction is that a desired high-degree compaction of the pressed product, i.e. a high bale density, is only achieved with an appropriately high surface pressure, this being realizable with a given maximum pressure of the hydraulic system only if large-dimensioned hydraulic cylinders are used. Such hydraulic cylinders have a large volume which must be delivered or recirculated by hydraulic pumps within a short time. In order that this can be accomplished within a short cycle time (time elapsing from the beginning to the end of the press cycle, i.e. until the press can be refilled), which is requested by the users of the press, large-dimensioned electric drives for hydraulic pumps are required which, in turn, require a corresponding electrical infrastructure. At some press installation locations, this infrastructure is not available and can be retrofitted with only much effort.
If baling presses are equipped with a press shield that can be moved in horizontal direction, the press chamber is also filled through a lockable press chamber door. Herein, the press chamber is filled while the press shield is in its rear end position. Once the press chamber is filled with sufficient pressed product, so that it is no longer possible to insert further pressed product, the press chamber door is closed and the horizontally movable press shield moves forward and compresses the pressed product in front of the press shield to form a compressed bale. Where presses with a press shield that can be moved in horizontal direction are concerned, the guide of the press shield also presents a frequent source of failures and damage.
In particular, irregular filling or filling with differently compressible pressed product pieces may lead to damage to the guide of the press shield or even to a bending of the piston rod of the hydraulic cylinder, said piston rod driving the press shield. To achieve a desired high-degree compaction, horizontal baling presses also require a high surface pressure to be exerted on the bale surface. This, in turn, requires large-dimensioned hydraulic cylinders. In this respect, the requirements for the design of the electric drives for the hydraulic pumps are comparable in these presses as well.